Along with the trend for high integration of a semiconductor device, a wiring width or an isolation width required for a manufacturing process thereof is being miniaturized. In general, formation of a micro pattern involves forming a resist pattern by using a photolithography technique; and then etching various kinds of underlying thin films by using the resist pattern as an etching mask.
To form the micro pattern, the photolithography technique is important. However, the recent miniaturization of the semiconductor device has progressed to the extent that a dimension no greater than a resolution limit of the photolithography technique is required.
An example technique for forming the pattern no greater than the resolution limit is disclosed in Patent Document 1.
In Patent Document 1, a first photosensitive film pattern (hereinafter, referred to as “first resist pattern”) is formed, and the first resist pattern is baked, and then an oxide film is formed on the first resist pattern. Subsequently, a second photosensitive film pattern (hereinafter, referred to as “second resist pattern”) is formed between the first resist patterns, and a micro pattern is formed by etching an underlying thin film using the first and second resist patterns as an etching mask.
According to Patent Document 1, since the micro pattern is formed by using two exposure masks, it is possible to obtain a resolution two times or more than a case in which a micro pattern is formed by using one exposure mask. For this reason, it is possible to form the micro pattern below or equal to a resolution limit.
Further, a technique of forming an oxide film on a resist pattern is disclosed in Patent Document 2, for example.
In Patent Document 2, a method of forming a micro pattern below a resolution limit is not disclosed. However, disclosed is a technique in which an oxide film is formed on a resist pattern, so that a thinning phenomenon of the resist pattern can be avoided, and striation or wiggling can be prevented from occurring in the formed micro pattern.
Patent Document 1: Japanese Patent No. 2757983
Patent Document 2: Japanese Patent Laid-open Publication No. 2004-80033